This proposal describes a new techniqu e for the combined morphological and chemical imaging of living neuronal cells using the scanning electrochemical microscope (SECM). The SECM, one of the family of scanning probe microscopes, is unique in its ability to image both the topography and the chemistry of an interface with mu/m to sub-mu/m resolution. In this work the techniques of amperometry and fast-scan cyclic voltammetry, already well-established electrochemical techniques in the neurosciences, will be incorporated into the SECM so that chemical imaging of neurotransmitter release, oxygen concentration, and pH can take place concomitantly with topographical imaging. A new type of constant distance imaging technique based on the SECM probe impedance will be used and further developed in order to record cell morphology with sub-pm resolution. The long-term objective of this work is to take advantage of the functional imaging capabilities of this powerful new technique to study neuronal growth, synaptogenesis, and neurodegeneration. The specific aims of this proposed work are important steps toward this objective. First, the imaging ability of the SECM will be strengthened through a series of instrumental and methodological improvements. Second, methods will be developed for imaging neurotransmitter release during differentiation and growth of model neurons. Finally, the SECM probe will be used to generate reactive oxygen species (hydrogen peroxide and hydroxyl radicals: so that the effect of site-specific application of oxidative stress on neuronal development can be investigated. This work will establish the SECM as a viable and powerful technique for studies of neuronal development and degeneration. As such, the SECM may become an important tool for fundamental investigations of the etiologies of neurodegenerative diseases, especially those that involve changes in neurotransmitter function (e.g. Parkinson's Disease).